The present invention relates to an ink liquid supply system for an ink jet system printer.
Generally, in an ink jet system printer and, more specifically, in an ink jet system printer of the charge amplitude controlling type, the ink liquid is sent from an ink liquid reservoir to a nozzle under a predetermined pressure when print operation is performed. When the ink jet system printer ceases its operation, the ink liquid supply from the ink liquid reservoir to the nozzle is terminated.
In a system wherein the issuance of the ink liquid from the nozzle is gradually reduced when the ink jet system printer ceases its operation, there is a possibility that the ink liquid droops from the tip end of the nozzle. This will cause the system to operate erroneously or break down, since the insulation of the system can not be maintained.
Accordingly, it is required that the issuance of the ink liquid from the nozzle is suddenly terminated when the ink jet system printer ceases its operation. A typical system to perform sudden termination of the ink issuance from the nozzle is disclosed in U.S. Pat. No. 4,007,684 "INK LIQUID WARMER FOR INK JET SYSTEM PRINTER" issued on Feb. 15, 1977, wherein an electromagnetic cross valve is provided for controlling the supply direction of the ink liquid. When the ink jet system printer ceases its operation, negative pressure is created at the nozzle by the electromagnetic cross valve to return the ink liquid from the nozzle.
In the above-mentioned type of ink liquid supply system the ink liquid surface comes into contact with the air at the interior of the nozzle when the ink jet system printer is not performing a printing operation. Therefore, there is a possibility that the ink liquid may solidify within the nozzle. This will block the orifice of the nozzle when the ink jet system printer begins to operate after an interruption of the printing operation for a considerably long period of time.
In addition, the present inventors have discovered that stable ink issuance is rapidly obtained when the ink liquid is filled to the tip end of the nozzle at a time when the printer operation is not performed.
Accordingly, an object of the present invention is to provide an ink liquid supply system for an ink jet system printer.
Another object of the present invention is to provide an ink liquid supply system for an ink jet system printer, wherein ink liquid is filled to the tip end of a nozzle when an ink jet system printer ceases its operation.
Still another object of the present invention is to provide an ink liquid supply system for an ink jet system printer, which ensures rapid termination of ink issuance from a nozzle when the printing operation is terminated and ensures rapid initiation of stable ink issuance from a nozzle when the printing operation is initiated.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an electromagnetic cross valve is provided for selectively connecting a nozzle with an ink liquid supply conduit and an ink liquid drain conduit. The electromagnetic cross valve functions to supply ink liquid from an ink liquid reservoir to the nozzle via the ink liquid supply conduit when the ink jet system printer performs a printing operation. When the ink jet system printer ceases its operation, the electromagnetic cross valve functions to connect the nozzle with the ink liquid drain conduit, whereby the issuance of the ink liquid from the nozzle is suddenly terminated.
A pressure control means is disposed within the ink liquid drain system. The pressure control means has an opening for maintaining the internal pressure of the pressure control means at atmospheric pressure. The opening is held at the height identical with that of the tip end of the nozzle, whereby the ink liquid is filled to the tip end of the nozzle when the ink jet system printer ceases its operation. Fluid resistance means are dispoed within the pressure control means for preventing generation of negative pressure at the nozzle side when the nozzle is connected with the pressure control means.